Tinea capitis is fungal infection of the scalp. The incubation period is usually 10-14 days. It varies from mild scaling, to black-dot alopecia, to draining pustules, to an inflammatory mass of oozing and crusting called a kerion. In the US, 90% of infections are caused by T tonsurans.
CASES/YEAR
30,000 (US); 600,000 (Global)
AGENT TYPE
Fungi (Dermatophytes)
OTHER NAMES
Scalp ringworm; Scalp infection by Trichophyton tonsurans or Microsporum canis; Scalp infection by T. violaceum, T. rubrum, T. schoenleinii, M. audouinii, T. soudanense, T. yaoundei, or T. gourvilii; White piedra (Trichosporon species); Black piedra (Piedra hortae);
INCUBATION
Usually 10-14 days; [CCDM, p. 173]
INITIAL SYMPTOMS
Varies from mild scaling, to black-dot alopecia, to draining pustules, to an inflammatory mass of oozing and crusting called a kerion; [ID, p. 1163]
PRECAUTIONS
Standard; "Rare episodes of person-to-person transmission." [CDC 2007 Guideline for Isolation Precautions]
COMMENTS
In the US, 90% of infections are caused by T tonsurans. [5MCC-2020] In endothrix infections caused by T. tonsurans, arthrospores are found inside the hair shaft, and the hairs break off at the skin level giving a black-dot appearance. [PPID, p. 3205-6] Tinea capitis in the U.S. is mainly an infection of school-age African-American males by T. tonsurans. Microsporum canis, acquired from stray cats and other animals, is more common in other parts of the world. Kerions are treated effectively with griseofulvin. The addition of oral antibiotics and steroids does not make the kerions flatten any faster. Ectothrix infections (arthrospores both within the hair shaft and on its surface) include M. audouinii, M. canis, Microsporum distortum, and Microsporum ferrugineum. These infections are Wood light fluorescent, but in the US the Wood lamp is no longer useful in screening school children because most cases are caused by T. tonsurans. [ID, p. 1162-5] Deep-seated Trichophyton infections can cause erythema nodosum. [Guerrant, p. 951] A benefit of culturing is that one may identify an animal source that can be treated. [Merck Manual, p. 1034]
DIAGNOSTIC
KOH prep for hyphae & spores; Culture; M. canis fluoresces in Wood's light, but T. tonsurans does not; Since therapy takes 12 wks, it is important to document the fungal infection. Obtain specimen with a moistened cotton swab or a #15 blade. [ID]
SCOPE
Global; Black piedra is endemic to tropical areas of South America, southeastern Asia, and Africa; [CCDM, p. 228]
SIGNS & SYMPTOMS
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H lymphadenopathy
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S papules or plaques
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S pustule
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S skin or subcutaneous nodule
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S ulcer of skin
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*erythema nodosum
ENTRY
Skin or Mucous Membranes (Includes Conjunctiva)
RESERVOIR
Cattle, Goats and Sheep, Cats, Dogs, Horses, Human
RISK FACTORS
- Handle domestic animals
- Touch infected farm animals
REFERENCES FOR CASES/YEAR
1. (US) 600,000/20 = 30,000;
2. (Global) Tinea capitis was about 6% of dermatophyte infections in one study [PMID 17352722], 10% in a study in Tunisia (PMID 19207834], and 0.2% in a study in Japan. Averaging the 3 percentages = about 5%; 5% of dermatophytoses = 5% X 12 million = 600,000 cases;